buying a perfume
Tenacity and Perfume Strength
In our Sidmouth shop, there is always an interest in the longevity of a potential purchase; often accompanied
by the complaint that some scents "do not seem to last on my skin". So what is it about
perfumes - why is it that some seem to last and others don't? Well, in moment we're going to talk about
all important perfume strength, but first we need to delve a little into perfume chemistry.
Perfumes are made from aromatic (ie smelly) and volatile (ie they evaporate) oils, usually, but not
always, applied to the skin after having been diluted in a carrier of alcohol and water. But not all volatile
aromatics are made equal - while the mechanisms inside the nose and brain are not fully understood,
for some reason some smell stronger
than others. A comparison can be made by looking at our visual senses. For instance, for some reason
internal to our
sensory perception, the colour yellow appears brighter (ie stronger) than blue, even when at the same intensity
of light.
The same is true of some smells. Even though our noses are receiving the same number of molecules, some smells
appear stronger than others. (There is another aspect to "scents not lasting on me" too which deserves a quick
mention, namely that our brains discount the importance of 'background' smells and with half and hour or so
start to ignore them in favour of 'new information'. There is a tendency for the wearer to notice less what
they are wearing, although the scent will still be received by new acquaintances whose brains are receptive
to 'new information'.)
Additionally, each aromatic has a different rate of evaporation (its natural vapour
pressure). Citrus oils for example, consist of
very small molecules that find no difficulty in jumping away from their surroundings, and in perfumes they
are therefore very fugitive elements. This is why citrus elements are often used as top notes - they
give an immediate 'take off' to a scent, but because they evaporate easily they will have all evaporated in under
and hour and a solely citrus creation naturally struggles to
last on the wearer. Some top notes even last for only a matter of minutes! Perfumers get around this by adding
a fixative - a large complex molecule (like musk) that physically
acts like a cage and holds back some of the smaller 'top notes' which only find their way free later (we often
then have a compromise -
some heavy notes have to be included simply to hold the top notes in). The point here is that
irrespective of the dilution, some scents will last longer than others solely as a result of their ingredients
, and this has nothing to do with
concentration. The best thing you can do is test
it and see, but remember: buying a scent simply on its longevity is a bit like buying a wine based upon how long
it will keep you drunk! Like fine wine, it is true that some of the most delicate and exquisite scents
may not have the tenacity of cheaper alternatives.
This brings us on to the next question of dilution, but this again is not as straightforward as it may seem at
first take. While there is no standard nor legal definitions (a perfume house can call their scents what they like),
there are three basic levels of concentration for perfumes: Eau de Toilette (5%-20% concentration),
Eau de Parfum
(10%-30%), and Perfume Extract (20% - 40%). By sheer weight of jus, the Perfume Extract ought to outlast
the Eau de Toilette and in most cases will, but matters are far more subtle than first appears.
One complexity is that as the strength changes, the perfumer will also change the balance of the
components. An Eau de Toilette will typically have a ratio of Top, Middle and Base notes of 5:3:2
whereas an Eau de Parfum will be 4:3:3 and Perfume Extract 2:3:5. The much larger predominance of
complex, lower volatility oils in a Perfume Extract, and correspondingly less flighty top notes will ensure
that, irrespective of dilution, the perfume will last hours longer than an Eau de Toilette. How much
longer?
Well, consider that a top note can last as little as a few minutes, a heart note 2 - 4 hours, and a base
note all day, it can be seen that a extract made from 50% heavy oils is going to last 8 hours or longer compared
to an Eau de Toilette with just 20% base oils. But
longevity is not the only thing that's changing here. A perfume of extract strength with less top and heart notes is going
to smell softer, more subtle, more balanced and in some cases not as strong as an Eau de Toilette (if you
think about it,
this has to be the case - if the molecules evaporate easily they will can be detected but
will not last; whereas if they evaporate slowly they will last all day but be less detectable). So higher
concentration scents will generally last longer, but appear more gentle and subtle than their (cheaper) lower dilution forms.